Technical Field
Embodiments of the invention relate generally to image acquisition. Particular embodiments relate to x-ray imaging systems used for mammography.
Discussion of Art
Generally, x-ray imaging systems expose an x-ray detector, e.g., gamma photon scintillator or film, to an x-ray source, via a target object that is to be imaged. Attenuation or dispersion of photons emitted from the x-ray source within the target object produces a variegated image at the x-ray detector. This image then can be processed to ascertain radiopacity at various regions of the target object. For example, in mammography, where breast tissue is imaged, a region of higher than average radiopacity is understood to indicate the presence of a potentially pre-cancerous or cancerous lesion.
In medical imaging, it is generally desirable to minimize the size and intensity of an x-ray source, especially when imaging radiation-sensitive tissues such as breast tissue. In particular, it is desirable to minimize the radiation exposure needed to identify and localize, in three dimensions, regions of high radiopacity that could indicate precancerous cells. To accomplish this, a moving x-ray source may be used to provide a low x-ray dose to the target tissue while also obtaining volumetric detector data for use in localizing regions of high radiopacity. A moving x-ray source, however, presents a potential problem of image distortion along the x-ray source direction of motion.
As mentioned, it is also desirable to identify radiopaque areas in three dimensions. Describing or displaying a three-dimensional structure from a sequence of planar images obtained from different perspectives is referred to as “tomosynthesis.” The quality of tomosynthesis solutions depends upon the quantity and quality of planar images and on the total angle covered by the planar image array.
Tomosynthesis solutions generally can be categorized as “sharp” (providing relatively high resolution and fidelity of location within three dimensions) or “fast” (providing real-time or near-real-time imaging). For some types of medical imaging, such as mammography, sharp or fast solutions are exclusive choices. Fast tomosynthesis involves continuous source motion during exposure, therefore reducing signal transfer at higher frequencies, and loss of information, which precludes obtaining optimally sharp images. The fuzziness of fast tomosynthesis can be mitigated to some extent by a moving x-ray detector, however the final travel distance required for the detector eventually affects the possible imaging area due to positioning constraints of the patient/organ relative to the x-ray detector. Moreover, moving detectors typically require more complex mechanical assemblies and precise synchronization of mechanical parts, which increases system cost, as a whole.
In view of the above, it is desirable to provide apparatus and methods for moving source mammography that mitigates image distortion and provides for rapid image acquisition. Such apparatus and methods might also be helpful toward volumetric x-ray imaging, generally.